The present invention relates to dispensing apparatus for use in dispensing fluid products in an aerosol form.
Such a dispensing apparatus typically comprises a dispensing unit engagingly sealed to an upper end of a storage container in which product to be dispensed is held. In order to maintain consistent operation of the dispensing apparatus, as the contents of the storage container are dispensed to an atmosphere during actuation of the apparatus, an air vent is provided to allow air to enter the container in order to equalise the pressures inside and outside the storage container.
A problem with ventilating the container in this manner lies in the potential contamination of the product by contaminants in the ambient air which are drawn into the container. This is a particular problem where the product to be dispensed is a pharmaceutical product, a product with perishable ingredients or a product liable to microbial contamination.
EP 0 487 412 A1 discloses one solution to this problem. The ventilating means in this apparatus comprises a disc-like annular filter covering a vent opening in a sheath such that ambient air entering the storage container passes through the filter. A problem with the device of EP 0 487 412 A1 is that a different size of filter is required for each type and size of dispensing apparatus that is manufactured. A further problem lies in that the transverse arrangement of the filter across the sheath means that the apparatus is not suitable for use with all storage containers, especially those having narrow openings at their upper ends. A yet further problem with disc-like filters subsists in the difficulty of assembling them with the remainder of the apparatus. Such filters tend to be difficult to handle, especially by automated machines, and easily separated from the remainder of the apparatus.